1. Field of the Invention
The present invention relates to a communication system including a subscriber information storage device for storing subscriber information.
2. Description of the Related Art
Conventionally, one telephone number has been commonly assigned to one terminal unit (e.g., mobile phone). In contrast, a service for assigning a plurality of telephone numbers (for example, at most 3 telephone numbers) to one terminal unit has been recently proposed. Further, a proposal for assigning one telephone number to a plurality of terminal units has also been recently proposed.
Further, a technique for using pieces of subscriber information selectively depending on the situations, with use of a USIM that stores a plurality of pieces of subscriber information (IMSI) (see claim 1, paragraphs 0041, 0054 and 0055 of Japanese Patent Application Publication No. 2006-121334). With this technique, a plurality of pieces of subscriber information of different contractor names can also be stored in the USIM. Accordingly, it is possible, for example, to use subscriber information in personal name and subscriber information in corporate name selectively depending on the situations.
However, in the conventional technique as described above, since the USIM is installed in the terminal unit, the subscriber information is switched at the terminal unit.
Here, let us assume a case where a certain terminal unit is provided with the USIM in which subscriber information A (in personal name) and subscriber information B (in corporate name) are stored, and another terminal unit (transmission terminal) performs transmission to the certain terminal unit (reception terminal).
In the case where both the subscriber information A and the subscriber information B are active, when the transmission terminal performs transmission with the subscriber information A, the reception terminal receives the transmission with the subscriber information A. In the same way, when the transmission terminal performs transmission with the subscriber information B, the reception terminal receives the transmission with the subscriber information B.
Meanwhile, in the case where only the subscriber information A is active, when the transmission terminal performs transmission with the subscriber information B, the reception terminal cannot receive the transmission. In the same way, in the case where only the subscriber information B is active, when the transmission terminal performs transmission with the subscriber information A, the reception terminal cannot receive the transmission.
Accordingly, in the conventional technique as described above, the subscriber information used in transmission needs to coincide with the subscriber information used in reception. As a result, the degree of freedom in selecting subscriber information used in transmission or reception is low, and thus convenience of a user is decreased.